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Target Point (target + point)

Distribution by Scientific Domains

Medical Sciences	66%

Selected Abstracts

MRI-guided procedures in various regions of the body using a robotic assistance system in a closed-bore scanner: Preliminary clinical experience and limitations,

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 4 2010
Michael Moche MD
Abstract Purpose: To present the clinical setup and workflow of a robotic assistance system for image-guided interventions in a conventional magnetic resonance imaging (MRI) environment and to report our preliminary clinical experience with percutaneous biopsies in various body regions. Materials and Methods: The MR-compatible, servo-pneumatically driven, robotic device (Innomotion) fits into the 60-cm bore of a standard MR scanner. The needle placement (n = 25) accuracy was estimated by measuring the 3D deviation between needle tip and prescribed target point in a phantom. Percutaneous biopsies in six patients and different body regions were planned by graphically selecting entry and target points on intraoperatively acquired roadmap MR data. Results: For insertion depths between 29 and 95 mm, the average 3D needle deviation was 2.2 ± 0.7 mm (range 0.9,3.8 mm). Patients with a body mass index of up to ,30 kg/m2 fitted into the bore with the device. Clinical work steps and limitations are reported for the various applications. All biopsies were diagnostic and could be completed without any major complications. Median planning and intervention times were 25 (range 20,36) and 44 (36,68) minutes, respectively. Conclusion: Preliminary clinical results in a standard MRI environment suggest that the presented robotic device provides accurate guidance for percutaneous procedures in various body regions. Shorter procedure times may be achievable by optimizing technical and workflow aspects. J. Magn. Reson. Imaging 2010;31:964,974. ©2010 Wiley-Liss, Inc. [source]

Deep brain stimulation for dystonia: Patient selection and evaluation

MOVEMENT DISORDERS, Issue S3 2002
Jens Volkmann MD
Abstract Deep brain stimulation (DBS) for dystonia still needs to be considered investigational, because there are no controlled studies for this indication, the optimal target point is uncertain, and long-term effects are unknown. The striking improvement of levodopa-induced dyskinesias in Parkinson's disease by deep brain stimulation of the internal pallidum has encouraged the use of this therapy for generalized and severe segmental dystonia in children and adults. Single case and small cohort studies have reported impressive efficacy of pallidal DBS in patients with primary dystonia, especially DYT1 mutation carriers, but results in secondary dystonia are less conclusive. This article discusses the different factors influencing patient selection for surgical treatment and describes standardized methods and the caveats for clinical documentation of treatment results in dystonia. © 2002 Movement Disorder Society [source]

Dyson's nonintersecting Brownian motions with a few outliers

COMMUNICATIONS ON PURE & APPLIED MATHEMATICS, Issue 3 2009
Mark Adler
Consider n nonintersecting Brownian particles on , (Dyson Brownian motions), all starting from the origin at time t = 0 and forced to return to x = 0 at time t = 1. For large n, the average mean density of particles has its support, for each 0 < t < 1, on the interval ±,2nt(1 , t). The Airy process ,,(,) is defined as the motion of these nonintersecting Brownian motions for large n but viewed from the curve ,, : y = ,2nt(1 , t) with an appropriate space-time rescaling. Assume now a finite number r of these particles are forced to a different target point, say a = ,0,n/2 > 0. Does it affect the Brownian fluctuations along the curve ,, for large n? In this paper, we show that no new process appears as long as one considers points (y, t) , ,, such that 0 < t < (1 + ,),1, which is the t -coordinate of the point of tangency of the tangent to the curve passing through (,0,n/2, 1). At this point the fluctuations obey a new statistics, which we call the Airy process with r outliers ,,(r)(,) (in short, r-Airy process). The log of the probability that at time , the cloud does not exceed x is given by the Fredholm determinant of a new kernel (extending the Airy kernel), and it satisfies a nonlinear PDE in x and ,, from which the asymptotic behavior of the process can be deduced for , , ,,. This kernel is closely related to one found by Baik, Ben Arous, and Péché in the context of multivariate statistics. © 2008 Wiley Periodicals, Inc. [source]

MRI-guided procedures in various regions of the body using a robotic assistance system in a closed-bore scanner: Preliminary clinical experience and limitations,

The role of cutaneous sensation in the motor function of the hand

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 4 2004
Ayman M. Ebied
Abstract We studied the effect of abolishing cutaneous sensation (by infiltrating local anaesthetic around the median nerve at the wrist) on the ability of 10 healthy volunteers (a) to maintain a submaximal isometric pinch-grip force for 30 s without visual feedback, and (b) to perform a fine finger-manipulation ,handwriting" task. Blocking cutaneous sensation had no effect on ability to maintain pinch force, suggesting that muscle afferents have the major role in force-control feedback. However, a near-linear fall in force, present with or without block (mean slope = ,1.3 ± 0.2% s,1), which cannot be attributed to motor fatigue, reveals a shortcoming of the afferent feedback system. Blocking cutaneous sensation did impair ability to perform the more demanding writing task, as judged by an 18 ± 6% increase in the length of the path between target points, a 22 ± 9% increase in the duration of the movement and a 63 ± 24% in ,normalised averaged rectified jerk", an averaged time-derivative of acceleration (all significantly nonzero, P < 0.04). These experiments demonstrate the relative importance of muscular and cutaneous afferent feedback on two aspects of hand performance, and provide a way to quantify the deficit resulting from the lack of cutaneous sensation. © 2003 Published by Elsevier Ltd. on behalf of Orthopaedic Research Society. All rights reserved. [source]

Skeleton-based active catheter navigation

THE INTERNATIONAL JOURNAL OF MEDICAL ROBOTICS AND COMPUTER ASSISTED SURGERY, Issue 2 2009
Yili Fu
Abstract Background The emergence of the active catheter has prompted the development of catheterization in minimally invasive surgery. However, it is still operated using only the physician's vision; information supplied by the guiding image and tracking sensors has not been fully utilized. Methods In order to supply the active catheter with more useful information for automatic navigation, we extract the skeleton of blood vessels by means of an improved distance transform method, and then present the crucial geometric information determining navigation. With the help of tracking sensors' position and pose information, two operations, advancement in the proximal end and direction selection in the distal end, are alternately implemented to insert the active catheter into a target blood vessel. Results The skeleton of the aortic arch reconstructed from slice images is extracted fast and automatically. A navigation path is generated on the skeleton by manually selecting the start and target points, and smoothed with the cubic cardinal spline curve. Crucial geometric information determining navigation is presented, as well as requirements for the catheter entering the target blood vessel. Using a shape memory alloy active catheter integrated with magnetic sensors, an experiment is carried out in a vascular model, in which the catheter is successfully inserted from the ascending aorta, via the aortic arch, into the brachiocephalic trunk. Conclusions The navigation strategy proposed in this paper is feasible and has the advantage of increasing the automation of catheterization, enhancing the manoeuvrability of the active catheter and providing the guiding image with desirable interactivity. Copyright © 2009 John Wiley & Sons, Ltd. [source]